Ball-mill for crushing ores



M. VOGEL-JRGENSEN. BALL MlLL FOR cRusHlNG GRES APPLICATION FILED AUG.20, 1919.

Patented Apr. 12, 1921.

I WITNESS! UNITED STATES PATENT OFFICE.

MIKAEL VOGEL-JQRGENSEN, OF FREDERIKSBERG, NEAR COPENHAGEN, DENMARK, ASSIGNOR TO F. L. SMIDTH & CO., 0F NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

To all whom t ma/y concern:

Be it known that I, MIKAEL Voorn-Jpn- GENsEN, civil-engineer, a subject of the Km of Denmark, residing in 103 Nyelandsve],

Frederiksberg, near Copenhagen, Denmark,

down to the desired ineness. The balls as aY rule are rather large and together with the material 'to be treated occupy 'so much room in the drum that the surface of the charge is at a level with the lower edge of the outlet pivot. The working of the mill requires a very considerable accumulation of material in the same, seeing that the ore having been treated is to be iushedout through the outlet pivot with water, and the means, therefore, whereby the crushing iineness is being regulated consists in varying the supply of l water in connection with variation of the quantity of material being fed into the mill.

Mills of the said kind are often furnished with a small conical sieve in the outlet, but this sieve is too inaccessible and its sifting area proper is too small to make it act as a regulator for the fineness. The sieve practically only serves like lSome .sort of controller, to iix a limit for the coarseness of the goods having been sifted 0H, but otherwise it has no iniuence on the degree of crushing.

In treating ore the grindingmust preferably be carried on very far, regardless of whether the ore is to be subjected to a following washing out on tables, or separation by means of otation, or magnetic separation, and when the whole of this comprehensive 'crushing as decribed is to be done by a ball mill alone, so that this actually has to also perform the total iine grinding, it really means that a task is exacted from such a Specication of Letters Patent. Patented Apr, 12, 1921, Application illed August 20, 1919. Serial No. 318,789. l i

mill for which it is not adapted at all'. Fur

mills, and little by little several improved types of ball mills for crushing ores have been constructed in which it has been successfully tried in various ways to obtain a better working. It has for instance been proposed to construct the mill with a large conical sieve widening toward the mill body and being made in one with the outlet bottom, forming part of this, whereby partly the accumulation of materials is reduced and partly the sifting effect improved, but besides the fact that even in a mill of this said construction the material will accumulate as described there is the further drawback in connection with the sifting that the material will have to pass out onto'the sieve and, as far as the part is concerned which is not fine enough to pass through this, back to the mill by the same way.4 lFor this reason a sieve of this description does not work in sufficiently effective way.

In some later types of ore Crushers sieves are arranged differently in the outlet bottom, but also in these mills the crushing ineness is regulated by accumulation of the material, the workinggtaking place by having the outlet grates covered to a suitable extent from the periphery toward the center whereby the material will accumulate and the iineness of crushing consequently be increased. l

Both of the drawbacks mentioned: the accumulation of material and the loading of the mill for an operation for which it is not adapted, the iine grinding, are present also in the later mills. Finally, it applies to` all these mills in common that the sifting always presents the drawback'as mentioned in the foregoing that the material which cannot pass through the sieve must return to the mill chamber by the same way by which it went out onto the sieve and, consequently, will render the passage for new material to be sifted difficult, whereby the sieve will be restraine-d from acting fully in such a way that it is this which regulates the ineness of crushin Even in the best of these later types o mills it has not been possible to prevent part of the material from being crushed down to the fineness of slurry before it leaves the mill, and in this condition the material is unqualified `for the purpose for which it is to be used.

The present invention has for its object firstly to limit the function of the mill to its real specialty, the crushing, and secondly to fit up the slfting system for separating -off the sufliciently crushed material in such a way that the sieve will actually act as the desired regulator for the crushing lineness. For the irst purpose the mill is furnished with an outlet bottom having peripherically arranged slits through which the material leaves the mill without having been sift/ed as soon as it has traveled through the drum, and for the second purpose, the attainment of an etlicient sifting action, a special arrangement has been made by means of which the material is led onto a sieve and back from the same by various paths in a continuous. course, a circulation .being arranged from the mill through arsifting drum and by another path from this ,back to the mill.

The accompanying drawin illustrates an embodiment of the outlet wa l of a mill according ,to the present invention, in lon itudinal section. The continuous exit-of t e material from the mill as soon as it has traveled through .the` -same is executed through wide grate intervals or slitsfc in the outlet wall b.' These intervals or slits c are placed as near as possible to the outer circumference of the mill in order to avoid an accumulation of material. The material having left the crushing chamber is taken upward byI means of lifting shovels Z and through a hole in the end of the hollow outlet tube u of the mill falls down on to a relatively coarse conical sieve s where the sufiiclently finely crushed material is sifted off. The part not yet fine enou h falls down the screen 1ntc a trough s an on other lifting shovels t. The shovels t transfer the material through channels t to a pipe /v which extends co-axially with the trunnion b. The discharge pipe u extends through the p1pe c. The inner end of the pipe c communicates with the interior of the mill so that the coarse material discharged into said p1pe is returned therethrough to the mill traveling in al direction contrary to the direction of travel of the material through the pipe u. The mill is supported by the hollow trunnion b journaled in a bear- 1n m. he quantity of water required for thesifting and for keeping the sieve clean is fed into the sieve cylinder through a pipe r which leads the water to the lifting shovels t and thus into the mill, so that the requisite amount of water for crushing is always present in the -mill chamber.

I claim as my invention: l. In a grinding mill, in combination with a supporting trunnion for the mill at the discharge end 1n open communication with the mill, but extending beyond the end wall thereof, a rate adjacent the discharge head through wich the material is discharged, a discharge pipe extending through the trunnion and adapted to receive the material from the grate and to convey it beyond the end of the trunnion, a screen supported at the end of the discharge trunnion to receive the material from the discharge pipe, and means to return .the coarse material from the screen to the trunnion whence it is conveyed therethrough in a direction counter to the direction of travel through the .dischar e pipe for return to the mill.

2. n a grinding mill, in combination with a ,supporting trunnion for the mill at the discharge end in open communication with the mill, but extending beyond the end wall thereof, a grate adjacent the discharge head through which the material is discharged, a discharge pipe extending through the trunnion `and adapted to receive the material from the grate and to convey it beyond the c.

pipe, a screen supported at the end of the discharge trunnion to receive the material from the discharge pipe, a trough formed at one end of the screen to receive the coarse material, lifting shovels in the trough and return channels extending from the shovels to the trunnion for the transfer of coarse material from the screen to the trunnion whence it is conveyed therethrough in a direction counter to the direction of travel thiicliugh the discharge pipe for return to the m1 3. In a grinding mill, in combination with a trunnion at the discharge end in open communication with the mill, a rate adjacent the discharge head through w ich the material is discharged, a discharge pipe mounted vcoaxially within the discharge 'end trunnion ported on the end of the discharge trunnion s said material passing through the trunnion and rotatable therewith to receive the ma' around the discharge pipe into the mill. 10 terial from the discharge ipe, a trough This specification signed and witnessed formed at the inner end of t e screen to rethis 12 day of April A. D. 1919.

5 ceive the coarse material, lifting shovels in MIKAEL VOGEL-JQRGENSAEN.

the trough and return channels extending Signed in the presence of from the shovels to the trunnion for the re- A. FoRsTnNsPAN,

turn of coarse material to the trunnion, E. Wmrsliow. 

